1. Field of the Invention
This invention relates to a two-stage hydrorefining process for heavy hydrocarbonaceous oils.
2. Description of the Prior Art
Hydrorefining is a well known process for upgrading hydrocarbonaceous oils by contacting the oils with added hydrogen in the presence of a catalyst to eliminate or reduce the concentration of contaminants in the oil such as sulfur compounds, nitrogenous compounds, and metal contaminants and/or partial saturation of the oil.
Multistage hydrodesulfurization processes are known in which the hydrogen sulfide and ammonia are removed between stages. See, for example, U.S. Pat. No. 3,717,571, and 3,847,799.
U.S. Pat. No. 4,048,060 discloses a two-stage hydrodesulfurization process in which a first stage catalyst and a second stage catalyst comprise Group VIB and Group VIII metal components. Hydrogen sulfide produced in the first hydrotreating zone may be removed between stages (see column 5, line 22).
It has now been found that for hydrorefining heavy hydrocarbonaceous oils containing certain types of organic sulfur compounds, a two-stage process utilizing a specific sequence of catalysts with interstage removal of hydrogen sulfide and ammonia will provide advantages that will become apparent in the ensuing description.